It is known that electrons travel without being scattered and behave like electrons in a vacuum by decreasing the size of a semiconductor up to a dimensional region smaller than the mean free path of electrons in the semiconductor. The conduction electrons are referred to as ballistic electrons that can travel without being scattered or with no loss even in a solid differently from normal conduction electrons based on drift or diffusion.
Because it is estimated that the semiconductor device technology is greatly innovated when ballistic electrons can be obtained at a high controllability, various studies about characteristics of ballistic electrons in the nanostructure of a semiconductor have been performed so far. However, most of the studies remain at physical observation under a very restricted condition such as a specific single structure or very low temperature and thus, they have not resulted in the industrial device development. To generate ballistic electrons for practical use, studies on material configurations and the material process technology are indispensable. However, it is the present state that there is almost no research or development obtaining excellent results from the above viewpoint.
A CRT (Cathode Ray Tube) and a fluorescent-character display tube are widely practically used as self-light-emitting display devices. These devices respectively conform to an operation principle of accelerating ejected electrons in vacuum by an electric field and excitating the fluorescent material coated on an opposite screen. Therefore, it is indispensable to include a vacuum tube having a certain volume or more for configuration. Therefore, this has been a large fault against decrease of a device in thickness or increase of the device in size.
Moreover, other self-light-emitting display devices include a display device using an EL element made of an inorganic or organic material and a plasma display.
The display device using the EL element conforms to an operation principle of accelerating carriers in a solid and collision-exciting the emission center. Therefore, the emission quantum efficiency is restricted to a limited value by an energy loss in the photon conversion of carriers in the solid and therefore, heat generation in the element is unavoidable. Therefore, to increase a display device in size, actions for deterioration of device characteristics due to a temperature rise and for thermal sinking are left as technical problems.
Also concerning a plasma display, restriction of emission due to energy loss under operation is a problem and moreover, the fact that it is difficult to realize small-power driving because of using discharge is left as a problem to be solved.
Thus, a natural-light display device has advantages and disadvantages depending on its type and has many technical subjects such as increase in size, decrease in thickness, and decrease in power consumption. However, when it is possible to obtain the ballistic electrons at a high controllability, it is expected that these technical problems are solved.
The present invention is made to solve the above problems and its object is to provide a method capable of generating ballistic electrons at a high controllability, a semiconductor device having a practical material configuration for the method, and display means using the semiconductor device.